Quenching of pyrene fluorescence by oxygen was used to determine oxygen diffusion coefficients in phospholipid dispersions and biological membranes. The diffusion coefficients at 37 degrees C are 1.5 x 0 to the negative fifth power centimeters squared /sec in dimyristoyl lecithin vesicles, 9.3 x 10 to the sixth power centimeters squared /sec in dipalmitoyl lecithin vesicles and 7.27 x 10 to the negative sixth power centimeters squared /sec in erythrocyte plasma membranes. We are now investigating how changes in membrane structure affect oxygen permeability. It is of great interest to note that general anesthetics alter the membrane structure to increase oxygen diffusion, as well as increasing the rotational and lateral diffusion of fluorescent hydrocarbons. The changes induced by general anesthetics alter the proton magnetic resonance spectra and relaxation times of phospholipid dispersions. We interpret the increase in diffusional rates of oxygen and hydrocarbons and NMR spectra as being due to change in the phopholipid packing. Other parameters which are likely to affect oxygen diffusion include the temperature, protein content and lipid composition of membranes. BIBLIOGRAPHIC REFERENCES: McDonald, G.G. and Vanderkooi, J.M. (1975) Biochemistry 14, 2125-2127 "Self-Diffusion of Phospholipid Vesicles Measured by Pulsed-Gradient Fourier Transform Nuclear Magnetic Resonance". Andrich, M. and Vanderkooi, J.M. (1976) Biochemistry, in press. "Temperature Dependence of 1,6-diphenyl-hexatriene Fluorescence in Artificial Membrane Systems"